Colleen L. Barry, an associate professor in the Department of Health Policy and Management at the Bloomberg School and senior author of the study, noted:

“Prescription drug abuse and deaths due to overdose have emerged as national public health crises. As our awareness of the addiction and overdose risks associated with use of opioid painkillers such as Oxycontin and Vicodin grows, individuals with chronic pain and their medical providers may be opting to treat pain entirely or in part with medical marijuana, in states where this is legal.”

“In absolute terms, states with a medical marijuana law had about 1,700 fewer opioid painkiller overdose deaths in 2010 than would be expected based on trends before the laws were passed,” said study’s lead author Marcus Bachhuber, researcher at the Philadelphia Veterans Affairs Medical Center and the University of Pennsylvania. He told Reuters:

“It certainly can be said that marijuana is much less toxic than opiates like Percocet or morphine, and that it is basically impossible to die from an overdose of weed. Based on those agreed-upon facts, it would seem that an increased use in marijuana instead of opiates for chronic pain is the most obvious explanation of the reduction in overdose deaths.”

Opioid overdose deaths across the country increased dramatically from 4,030 in 1999 to 16,651 in 2010. Of those who died from prescription opioid overdoses, 60% had a legitimate prescription from a single doctor. Opioid analgesics, such as oxycodone, hydrocodone, and methadone, were involved in about 3 of every 4 pharmaceutical overdose deaths.